For nanomaterials made of crystals of dimensions on the order of a few nanometers, material properties frequently depend on crystal size. For nanocrystals, there is a tendency to metastability that is dependent on nanocrystal processing conditions. Nanocrystals of the same stoichiometry and size may exhibit different crystal structures. Because nanocrystal structure partially determines nanomaterial properties, methods that provide information on crystal structures are important for the effective use and fabrication of nanomaterials.
One conventional method of structure identification is based on powder X-ray diffraction. In powder X-ray diffraction fingerprinting, three-dimensional (3D) crystal structure information is collapsed into a one-dimensional intensity profile as a function of scattering angle or reciprocal lattice vector. Bragg diffraction peaks in such diffractograms provide fingerprint information. Unfortunately, powder X-ray methods are of limited usefulness for identifying crystal structures in the nanometer size range. In addition, some technologically important nanomaterials such as, e.g., vanadium-oxide nanotubes, do not produce characteristic powder X-ray diffraction fingerprints. Thus improved identification methods for nanocrystals are needed.